1. Field of the Invention
The invention relates to wireless communications. More particularly, the invention relates to methods and apparatus for combined wireless data and voice communications using the same frequency spectrum.
2. Brief Description of the Prior Art
One of the important socioeconomic changes of the last decade is the rising preponderance of the “home office”. Largely because of advances made in personal computer technology, people are now able to work at home doing things which once required that they travel to an office. People who work in an office, now take the opportunity to bring work home. This allows them to spend more time with their family without adversely affecting their productivity. The home office revolution has also given rise to an increasing number of home businesses in which the home office is the only office.
The typically well equipped home office today includes one or more personal computers, a laser printer, a fax machine, a photocopier and two or more phone lines. As a home office grows, it is desirable to connect the computers and printers to a network and increase the number of telephones and telephone lines. In a commercial office building, wiring for networks and telephones is either pre-installed or easy to install via preinstalled closets and conduits. Most homes, however, are not pre-wired for a computer network, nor are they pre-wired for more than two telephone lines.
Recognizing the difficulty presented for home office networks, several major technology vendors have proposed various wireless solutions. There are two major wireless standards. One, proposed by Lucent Technologies and Apple Computer is known as IEEE 802.11 Direct Sequence Spread Spectrum (DSSS) and supports data rates of up to 11 megabits per second at distances up to 150 feet. It is sold under the trademarks “AirPort” and “Skyline”, among others.
The other wireless standard, which is supported by a long list of technology companies including IBM, Xerox, and Intel, to name a few, is known as “HomeRF” or SWAP (Shared Wireless Access Protocol). HomeRF has the same 150 foot range as IEEE 802.11 but initially only supported a data rate of up to 2 megabits per second. The specification for HomeRF was recently revised to support 10 megabits per second.
Both HomeRF and IEEE 802.11 utilize the 2.4 gigahertz band for wireless communications and manage network access via CSMA (carrier sense multiplex access). In a typical setup, a base station transceiver is coupled to a telecommunications link such as a telephone line, a DSL modem, or a cable modem and computers are provided with transceiver cards which allow them to share the communications link and communicate with each other via the base station.
Both HomeRF and IEEE 802.11 offer cost efficient solutions for networking computers and printers without wires and should be popular in home offices. However, neither of these wireless networking standards addresses the need for more phones and phone lines in a home office. Many home offices use cordless telephones to avoid the need for wiring new phones and new phone lines.
Recently a new class of cordless telephones has been developed. These new phones are based on the DECT (Digitally Enhanced Cordless Telecommunications) standard and offer many of the features previously only available in an office PBX system.
Siemens Corporation has introduced a proprietary version of DECT based telephones called WDCT (Worldwide Digital Cordless Communications). Hardware to support WDCT is commercially available from Infineon Technologies, AG which manufactures, for example, transceivers for 2.4 GHz cordless applications (WDCT Transceiver PMB5614), a WDCT handset controller and a WDCT basestation controller. The Siemens telephone sets include a base station transceiver, which is coupled to telephone lines and cordless handsets which access the telephone lines by communicating with the base station transceiver. The base station transceiver supports multiple phone lines and multiple hand sets.
WDCT telephones operate in the 2.4 gigahertz band. Access under WDCT is governed by a repeating TDM (Time Division Multiplexing) frame during which specific time slots are allocated for transmission and reception. Since the new cordless telephones operate in the same band as the new wireless networks, it is important that the respective base stations be placed far enough apart that they do not interfere with each other.
One of the problems faced by home offices is space. Many home offices occupy a spare bedroom or a den and the space soon feels cluttered with office equipment. Many companies have addressed this problem in a number of ways. Personal computers have become smaller. Many companies now offer a combination printer, scanner, copier, fax machine which is a single unit that takes the place of four separate units.
Similarly, it would be desirable to provide a single wireless base station to serve all of the wireless networking needs of a home office. However, since the new cordless telephones operate in the same band as the new wireless networks, it prohibits providing a single base station transceiver which could be used for cordless telephones as well as for wireless networking.